Borane-functionalized oxide supports: development of active supported metallocene catalysts at low aluminoxane loading

Treatment of hydroxylated silica or alumina with tris(perfluorophenyl)boran e (1), bis(perfluorophenyl)borane (2) or bis(perfluorophenyl)boron chloride (3), provides borane-functionalized supports of variable composition, as r evealed by in situ monitoring by F-19 NMR spectroscopy and/or elemental ana lysis. These chemically treated supports can be impregnated with Cp2ZrMe2 t o provide supported catalysts for ethylene polymerization. Although some of these supported catalysts are active for ethylene polymerization in the pr esence of alkylaluminum compounds (e.g., TMA, TIBAL), all of these catalyst s are more efficiently activated in the presence of small quantities of met hyl aluminoxane, even at very low Al:Zr ratios of 10:1. The polymer propert ies are quite similar to those produced using the soluble catalyst Cp2ZrMe2 /B(C6F5)(3), again in the presence of MAO at low loading. A variety of expe riments suggest that minimal leaching of the metallocene complex from the s upport occurs under the conditions studied; in particular, production of po lyethylene with high bulk densities (> 0.2 g/cm(3)) and little reactor foul ing, even at elevated temperature in toluene slurry, is observed. (C) 1999 Elsevier Science B.V. All rights reserved.